1. Technical Field
This invention relates to lances such as used for introducing an inert gas into molten metal for stirring the same or for injecting a stream of oxygen into molten metal for refining the same.
2. Description of the Prior Art
Lances for introducing gases into molten metal for various purposes are disclosed in U.S. Pat. Nos. 3,379,428 and 3,082,997, which disclose immersion lances formed of straight metal tubes forming a plurality of gas conduits arranged to direct gas downwardly into the molten metal in which the lance is positioned.
U.S. Pat. Nos. 3,645,520 and 3,898,078 disclose lances in which the gas conveying conduits are formed in several patterns, the U.S. Pat. No. 3,645,520 providing an axial metal conduit around which several tubes are spirally wound and encased in an exterior housing which may be a protective refractory.
Alternate forms of the disclosure position the metal tubes in various patterns and surrounds them with a refractory body and one such form adds an exterior housing, partly metal and partly refractory.
U.S. Pat. No. 3,898,078 forms the lance of a pair of tubular members, one positioned within the other with the inner tubular member having a relatively thick end portion in which helical passageways are formed so that gas introduced into an area between the tubular members will flow through the helical passageways which communicate with the delivery end of the lance. The lower portion of this end of the lance is covered with a suitable refractory.
U.S. Pat. Nos. 4,389,245 and 4,550,898 disclose lances having straight gas conveying conduits therein and refractory housings of cylindrical cross section thereabout and U.S. Pat. No. 4,588,170 discloses a lance which is primarily an elongated refractory body having a tubular gas conduit extending longitudinally thereof and terminating inwardly of the ends thereof in a cavity opening inwardly.
The present invention relates to a substantially improved lance for treating molten metals in which the principal body of the lance is formed of a refractory material with a bore extending longitudinally through a portion of the refractory material and terminating inwardly of the delivery end of the lance where it communicates with a plurality of smaller metal tubes preferably arranged in a circular pattern in which the smaller metal tubes are spirally positioned, each of the smaller metal tubes being shaped such as partially flattened to form a metered passageway of a desired size, the distal ends of the smaller metal tubes communicate with the delivery end of the lance so that most of the gas flowing through the smaller metal tubes will be delivered into the molten metal in a spiral swirling pattern in a predetermined amount at a predetermined pressure. The bore in the principal body member of the lance is preferably a metal tube communicating with the plurality of smaller metal tubes at one of its ends and extending outwardly of the refractory body of the lance at its other end. The diameter of the bore, about 11/2", and the outer diameter of the metal tube, about 11/2", are less than or equal to one-fourth of the side to side dimensions, about 10", of the refractory body of the lance.
The novel construction of the bore in the relatively thick refractory body of the lance utilizing the metal tube and the plurality of smaller metal tubes extending from the same to the delivery end of the lance enables the lance to be more effectively used in introducing gas into molten metal and contributes to its substantially longer life than has heretofore been possible with the prior art lances as an additional pattern of bubbling gasses in the molten metal envelopes the refractory material of the body of the lance and the relatively thick refractory body of the lance protects the metal tubes from rapid failure.